Sliding range gate for large area ultrasonic sensor

ABSTRACT

An apparatus includes an ultrasonic sensor array and a sensor controller. The sensor array includes a plurality of ultrasonic sensor pixels, each sensor pixel including an ultrasonic receiver and a receiver bias electrode and being operable in one or both of a transmit mode of operation or a read mode of operation. The sensor controller is electrically coupled with the receiver bias electrodes. The sensor controller is configured to set, at each sensor pixel, a range gate window (RGW) by modulating a bias voltage applied to the receiver bias electrode and to set, for a first portion of the ultrasonic sensor pixels, a first RGW. The sensor controller is configured to set, for a second portion of the ultrasonic sensor pixels, a second RGW, and establish a first temporal delay between the first RGW and the second RGW.

PRIORITY CLAIM

This disclosure claims priority to U.S. Provisional Patent ApplicationNo. 62/565,479, filed on Sep. 29, 2017, entitled “SLIDING RANGE GATE FORLARGE AREA ULTRASONIC SENSOR,” assigned to the assignee hereof andincorporated herein by reference in its entirety. The presentapplication may also be considered to be related to co-pending U.S.patent application Ser. No. 15/827,529, filed on Nov. 30, 2017, entitled“LAYER FOR INDUCING VARYING DELAYS IN ULTRASONIC SIGNALS PROPAGATING INULTRASONIC SENSOR,” and co-pending U.S. patent application Ser. No.15/827,528, filed on Nov. 30, 2017, entitled “SYSTEM AND METHOD FORULTRASONIC SENSING,” both assigned to the assignee hereof.

TECHNICAL FIELD

This disclosure relates to ultrasonic transducer arrays and, moreparticularly to a large area array of ultrasonic transducersincorporating a sliding range gate.

DESCRIPTION OF THE RELATED TECHNOLOGY

Ultrasonic sensor systems may use a transmitter to generate and send anultrasonic wave through a transmissive medium and towards an object tobe detected and/or imaged. The ultrasonic transmitter may be operativelycoupled with an ultrasonic sensor array configured to detect portions ofthe ultrasonic wave that are reflected from the object. At each materialinterface encountered by the ultrasonic pulse, a portion of theultrasonic pulse may be reflected. In some implementations, anultrasonic pulse may be produced by starting and stopping thetransmitter during a short interval of time (e.g. less than 1microsecond). An ultrasonic sensor system may include biometric sensors,such as fingerprint or handprint sensors, and/or other ultrasonicimaging applications.

Piezoelectric ultrasonic transducers are attractive candidates for suchapplications and may include piezoelectric micromechanical ultrasonictransducers (PMUTs) configured as a multilayer stack that includes apiezoelectric layer stack. The piezoelectric layer stack may include alayer of piezoelectric material such as, for example, a layer ofpolyvinylidene fluoride (PVDF) or a PVDF copolymer. The piezoelectriclayer may convert vibrations caused by ultrasonic reflections intoelectrical output signals. In some implementations, the ultrasonicsensor system further includes a thin-film transistor (TFT) layer thatmay include an array of sensor pixel circuits that may, for example,amplify electrical output signals generated by the piezoelectric layer.

In some applications, a two-dimensional array of a large number of PMUTelements (a “PMUT array”) may be contemplated. For example an array of1-5 million PMUTs may be contemplated for some large area ultrasonicsensors. In the absence of the presently disclosed techniques, the TFTlayer of such a large area ultrasonic sensors may limit the current tothe pixel elements and degrade transmission of the signals generated bythe piezoelectric layer, due to narrow pixel to pixel address and signaltraces.

As a result, improved PMUT drive/readout schemes are desirable,particularly for large PMUT arrays.

SUMMARY

The systems, methods and devices of this disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein.

One innovative aspect of the subject matter described in this disclosurerelates to an ultrasonic sensor array including a plurality ofultrasonic sensor pixels, each sensor pixel including an ultrasonicreceiver and a receiver bias electrode and being operable in one or bothof a transmit mode of operation or a read mode of operation and a sensorcontroller electrically coupled with the receiver bias electrodes. Thesensor controller is configured to set, at each sensor pixel, a rangegate window (RGW) by modulating a bias voltage applied to the receiverbias electrode. The sensor controller is configured to set, for a firstportion of the ultrasonic sensor pixels, a first RGW. The sensorcontroller is configured to set, for a second portion of the ultrasonicsensor pixels, a second RGW, and establish a first temporal delaybetween the first RGW and the second RGW.

In some examples, the apparatus may be configured to establish atemporal phasing of acoustic signals returned, as a result ofinteraction with a target object, to the ultrasonic sensor array suchthat the first portion of the ultrasonic sensor pixels receives thereturned acoustic signals at a different time than the second portion ofthe ultrasonic sensor pixels. In some examples, the ultrasonic receiversmay be disposed in a receiver array layer, the ultrasonic sensor arraymay include ultrasonic transmitters disposed in a transmitter arraylayer, and the receiver array layer is not parallel with the transmitterarray layer. In some examples, a non-uniform separation between thereceiver array layer and the transmitter array layer may establish thetemporal phasing of the returned acoustic signals. In some examples, theultrasonic sensor array may include ultrasonic transmitters disposed ina transmitter array layer, the transmitter array layer may be segmentedinto separate portions, and the sensor controller may be configured tocause the ultrasonic transmitters to launch acoustic signals, from theseparate portions, non-simultaneously so as to establish the temporalphasing of the returned acoustic signals.

In some examples, the first RGW may have a first RGW duration and thefirst temporal delay may be approximately 5-25% of the first RGWduration. In some examples, the first RGW duration may be between 200nanoseconds and 1000 nanoseconds.

In some examples, the first temporal delay may be approximately 25nanoseconds.

In some examples, the sensor controller may be configured to set, foreach of a plurality of portions of the ultrasonic sensor pixels arespective RGW and to establish a respective temporal delay between eachrespective RGW.

In some examples, the sensor controller may be configured to set, foreach of a plurality of portions the sensor controller is configured toset a respective range gate delay (RGD). In some examples, the RGD foreach portion, k+1, may be longer than the RGD for each portion, k, by atemporal delay period. In some examples, the first RGW may have a firstRGW duration and the temporal delay period is approximately 5-25% of thefirst RGW duration.

According to some implementations, for an ultrasonic sensor array,including a first portion of ultrasonic sensor pixels and a secondportion of ultrasonic sensor pixels, a method includes setting, with asensor controller, a first range gate window (RGW) for the first portionof ultrasonic sensor pixels, and setting, with the sensor controller, asecond RGW for the second portion of ultrasonic sensor pixels so as toestablish a first temporal delay between the first RGW and the secondRGW. Each sensor pixel includes an ultrasonic receiver and a receiverbias electrode and is operable in one or both of a transmit mode ofoperation or a read mode of operation. The sensor controller iselectrically coupled with the receiver bias electrodes, and setting thefirst RGW and the second RGW includes modulating a bias voltage appliedto the receiver bias electrode.

In some examples, the ultrasonic sensor array may be configured toestablish a temporal phasing of acoustic signals returned, as a resultof interaction with a target object, to the ultrasonic sensor array suchthat the first portion of the ultrasonic sensor pixels receives thereturned acoustic signals at a different time than the second portion ofthe ultrasonic sensor pixels.

In some examples, the method may further include setting, with thesensor controller, for each of a plurality of portions of the ultrasonicsensor pixels a respective RGW and establishing, with the sensorcontroller, a respective temporal delay between each respective RGW.

In some examples, the method may further include setting, with thesensor controller, for each of a plurality of portions of the ultrasonicsensor pixels, a respective range gate delay (RGD). In some examples,the RGD for each portion, k+1, may be longer than the RGD for eachportion, k, by a temporal delay period. In some examples, the first RGWmay have a first RGW duration and the temporal delay period may beapproximately 5-25% of the first RGW duration.

According to some implementations, for an ultrasonic array including afirst portion of ultrasonic sensor pixels and a second portion ofultrasonic sensor pixels, a non-transitory computer readable mediumstores program code to be executed by a sensor controller of theultrasonic sensor array, the program code comprising instructionsconfigured to cause the sensor controller to: set, with a sensorcontroller, a first range gate window (RGW) for the first portion ofultrasonic sensor pixels, and set, with the sensor controller, a secondRGW for the second portion of ultrasonic sensor pixels so as toestablish a first temporal delay between the first RGW and the secondRGW. Each sensor pixel includes an ultrasonic receiver and a receiverbias electrode and is operable in one or both of a transmit mode ofoperation or a read mode of operation. The sensor controller iselectrically coupled with the receiver bias electrodes and setting thefirst RGW and the second RGW includes modulating a bias voltage appliedto the receiver bias electrode.

In some examples, the ultrasonic sensor array may be configured toestablish a temporal phasing of acoustic signals returned, as a resultof interaction with a target object, to the ultrasonic sensor array suchthat the first portion of the ultrasonic sensor pixels receive thereturned acoustic signals at a different time than the second portion ofthe ultrasonic sensor pixels.

In some examples, the computer readable medium may further includeinstructions to cause the sensor controller to set, for each of aplurality of portions of the ultrasonic sensor pixels a respective RGWand establish a respective temporal delay between each respective RGW.

In some examples, the computer readable medium may further includeinstructions to cause the sensor controller to set, for each of aplurality of portions, a respective range gate delay (RGD). In someexamples, the RGD for each portion, k+1, may be longer than the RGD foreach portion, k, by a temporal delay period. In some examples, the firstRGW may have a first RGW duration and the temporal delay period may beapproximately 5-25% of the first RGW duration.

According to some implementations, an apparatus includes an ultrasonicsensor array including a plurality of ultrasonic sensor pixels, eachsensor pixel including an ultrasonic receiver and a receiver biaselectrode and being operable in one or both of a transmit mode ofoperation or a read mode of operation; and, electrically coupled withthe receiver bias electrodes, and means for controlling the ultrasonicsensor array, the means configured to: set, at each sensor pixel, arange gate window (RGW) by modulating a bias voltage applied to thereceiver bias electrode, set, for a first portion of the ultrasonicsensor pixels, a first RGW; and set, for a second portion of theultrasonic sensor pixels, a second RGW, and establish a first temporaldelay between the first RGW and the second RGW.

In some examples, the apparatus may be configured to establish atemporal phasing of acoustic signals returned, as a result ofinteraction with a target object, to the ultrasonic sensor array suchthat the first portion of the ultrasonic sensor pixels receives thereturned acoustic signals at a different time than the second portion ofthe ultrasonic sensor pixels. In some examples, the ultrasonic receiversmay be disposed in a receiver array layer, the ultrasonic sensor arraymay include ultrasonic transmitters disposed in a transmitter arraylayer, and the receiver array layer is not parallel with the transmitterarray layer. In some examples, a non-uniform separation between thereceiver array layer and the transmitter array layer may establish thetemporal phasing of the returned acoustic signals. In some examples, theultrasonic sensor array may include ultrasonic transmitters disposed ina transmitter array layer, the transmitter array layer may be segmentedinto separate portions, and the means for controlling the ultrasonicsensor array may be configured to cause the ultrasonic transmitters tolaunch acoustic signals, from the separate portions, non-simultaneouslyso as to establish the temporal phasing of the returned acousticsignals.

In some examples, the means for controlling the ultrasonic sensor arraymay be configured to set, for each of a plurality of portions of theultrasonic sensor pixels a respective RGW and to establish a respectivetemporal delay between each respective RGW.

BRIEF DESCRIPTION OF THE DRAWINGS

Details of one or more implementations of the subject matter describedin this specification are set forth in this disclosure and theaccompanying drawings. Other features, aspects, and advantages willbecome apparent from a review of the disclosure. Note that the relativedimensions of the drawings and other diagrams of this disclosure may notbe drawn to scale. The sizes, thicknesses, arrangements, materials,etc., shown and described in this disclosure are made only by way ofexample and should not be construed as limiting. Like reference numbersand designations in the various drawings indicate like elements.

FIG. 1 shows a front view of a diagrammatic representation of an exampleof an electronic device that includes an ultrasonic sensing systemaccording to some implementations.

FIG. 2A shows a block diagram representation of components of an exampleof an ultrasonic sensing system, according to some implementations.

FIG. 2B shows a block diagram representation of components of an exampleof an electronic device, according to some implementations.

FIG. 3A shows a cross-sectional of an example of an ultrasonic sensingsystem, according to some implementations.

FIG. 3B shows an enlarged cross-sectional side view of the ultrasonicsensing system of FIG. 3A, according to some implementations.

FIG. 4 shows an exploded projection view of an example of components ofan example ultrasonic sensing system according to anotherimplementation.

FIG. 5 illustrates a block diagram of an ultrasonic sensor system,according to an implementation.

FIG. 6 illustrates a simplified block diagram of a sensor pixel arraycoupled with pixel readout electronics.

FIG. 7, graphically illustrates an example of transmitter excitationsignals and receiver bias voltage levels as a function of time.

FIG. 8 illustrates an example of temporal phasing of receiver outputsignals, according to an implementation.

FIG. 9 illustrates an example of temporal phasing of transmission andreception of acoustic signals, according to an implementation.

FIG. 10 graphically illustrates an example of transmitter excitationsignals and receiver bias voltage levels as a function of time.

FIG. 11 illustrates a sliding range gate, in accordance with animplementation.

FIG. 12 graphically illustrates an example of transmitter excitationsignals and receiver bias voltage levels as a function of time, inaccordance with an implementation.

FIG. 13 graphically illustrates an example of transmitter excitationsignals and receiver bias voltage levels as a function of time, inaccordance with another implementation.

FIG. 14 illustrates an example of a process flow for operating anultrasonic sensor array.

DETAILED DESCRIPTION

The following description is directed to certain implementations for thepurposes of describing the innovative aspects of this disclosure.However, a person having ordinary skill in the art will readilyrecognize that the teachings herein may be applied in a multitude ofdifferent ways. The described implementations may be implemented in anydevice, apparatus, or system that includes a sensor system. In addition,it is contemplated that the described implementations may be included inor associated with a variety of electronic devices such as, but notlimited to: mobile telephones, multimedia Internet enabled cellulartelephones, mobile television receivers, wireless devices, smartphones,smart cards, wearable devices such as bracelets, armbands, wristbands,rings, headbands and patches, etc., Bluetooth® devices, personal dataassistants (PDAs), wireless electronic mail receivers, hand-held orportable computers, netbooks, notebooks, smartbooks, tablets, printers,copiers, scanners, facsimile devices, global positioning system (GPS)receivers/navigators, cameras, digital media players (such as MP3players), camcorders, game consoles, wrist watches, clocks, calculators,television monitors, flat panel displays, electronic reading devices(e.g., e-readers), mobile health devices, computer monitors, autodisplays (including odometer and speedometer displays, etc.), cockpitcontrols and/or displays, steering wheels, camera view displays (such asthe display of a rear view camera in a vehicle), electronic photographs,electronic billboards or signs, projectors, architectural structures,microwaves, refrigerators, stereo systems, cassette recorders orplayers, DVD players, CD players, VCRs, radios, portable memory chips,washers, dryers, washer/dryers, automated teller machines (ATMs),parking meters, packaging (such as in electromechanical systems (EMS)applications including microelectromechanical systems (MEMS)applications, as well as non-EMS applications), aesthetic structures(such as display of images on a piece of jewelry or clothing) and avariety of EMS devices. The teachings herein also may be used inapplications such as, but not limited to, electronic switching devices,radio frequency filters, sensors, accelerometers, gyroscopes,motion-sensing devices, magnetometers, inertial components for consumerelectronics, parts of consumer electronics products, varactors, liquidcrystal devices, electrophoretic devices, drive schemes, manufacturingprocesses and electronic test equipment. Thus, the teachings are notintended to be limited to the implementations depicted solely in theFigures, but instead have wide applicability as will be readily apparentto one having ordinary skill in the art.

In some implementations, ultrasonic sensor systems include piezoelectricmaterial for the transmission and receiving of ultrasonic waves.

For example, a voltage applied across piezoelectric materialcorresponding to a transmitter may result in the piezoelectric materialstretching or contracting, e.g., being deformed such that the materialis strained in response to the applied voltage, resulting in thegeneration of the ultrasonic wave, as previously discussed. Thereflected signals (e.g., the reflected portions of the ultrasonic wave,as previously discussed) may result in the stretching or contracting ofpiezoelectric material corresponding to a receiver. This results in thegeneration of a surface charge, and therefore, a voltage across thepiezoelectric material that may be used as an electrical output signalrepresenting a portion of raw image data that represents fingerprintimage data.

Some implementations of the subject matter described in this disclosureprovide circuitry for an ultrasonic sensing system. Features of relatedultrasonic sensing techniques are described in U.S. patent applicationSer. No. 15/292,057, filed Oct. 12, 2016, owned by the assignee of thepresent disclosure and entitled “INTEGRATED PIEZOELECTRICMICROMECHANICAL ULTRASONIC TRANSDUCER PIXEL AND ARRAY”, and in U.S.patent application Ser. No. 15/704,337, filed Sep. 14, 2017 owned by theassignee of the present disclosure and entitled “ULTRASONIC TRANSDUCERPIXEL READOUT CIRCUITRY AND METHODS FOR ULTRASONIC PHASE IMAGING”, thedisclosures of which are hereby incorporated by reference in theirentirety into the present application.

In some implementations, the ultrasonic sensing system includes an M×Narray of pixels, i.e., M rows by N columns of pixels. In someimplementations, values of M and N are each greater than 1000. Forexample, a 1200×1600 array of nearly two million pixels may becontemplated. As a further example, a 1600×1800 array of nearly threemillion pixels may be contemplated. It will be appreciated that,assuming a typical pixel spacing on the order of 400-600 pixels perinch, the ultrasonic sensing systems contemplated by the presentdisclosure can accommodate an imaging area on the order of 5-20 squareinches. Such large area ultrasonic sensing systems may be desirable forsimultaneous imaging of multiple fingerprints, palm or hand prints, forexample.

Some implementations of the subject matter described in this disclosuremay be practiced to realize one or more of the following potentialadvantages. The disclosed techniques introduce small temporal delaysbetween at least portions of outputted receiver signals. As a result, aload on the TFT layer signal traces may be significantly reduced largenumber of pixels may output receiver signals simultaneously or nearlysimultaneously with a result that at least some signals sufferdegradation due to limitations of the TFT layer signal traces. Inaddition, by implementing a sliding range gate window (RGW), timing ofthe RGW may be controlled so as to compensate for the temporal delays,provide that the RGW window remains well aligned in a desiredrelationship to returned acoustic signals.

FIG. 1 shows a front view of a diagrammatic representation of an exampleof an electronic device 100 that includes an ultrasonic sensing systemaccording to some implementations. The electronic device 100 may berepresentative of, for example, various portable computing devices suchas cellular phones, smartphones, multimedia devices, personal gamingdevices, tablet computers and laptop computers, among other types ofportable computing devices. However, various implementations describedherein are not limited in application to portable computing devices.Indeed, various techniques and principles disclosed herein may beapplied in traditionally non-portable devices and systems, such as incomputer monitors, television displays, kiosks, vehicle navigationdevices and audio systems, among other applications. Additionally,various implementations described herein are not limited in applicationto devices that include displays.

In the illustrated implementation, the electronic device 100 includes ahousing (or “case”) 102 within which various circuits, sensors and otherelectrical components may be disposed. In the illustratedimplementation, the electronic device 100 also includes a display (thatmay be referred to herein as a “touchscreen display” or a“touch-sensitive display”) 104. The display 104 may generally berepresentative of any of a variety of suitable display types that employany of a variety of suitable display technologies. For example, thedisplay 104 may be a digital micro-shutter (DMS)-based display, alight-emitting diode (LED) display, an organic LED (OLED) display, aliquid crystal display (LCD), an LCD display that uses LEDs asbacklights, a plasma display, an interferometric modulator (IMOD)-baseddisplay, or another type of display suitable for use in conjunction withtouch-sensitive user interface (UI) systems.

The electronic device 100 may include various other devices orcomponents for interacting with, or otherwise communicating informationto or receiving information from, a user. For example, the electronicdevice 100 may include one or more microphones 106, one or more speakers108, and in some cases one or more at least partially mechanical buttons110. The electronic device 100 may include various other componentsenabling additional features such as, for example, one or more video orstill-image cameras 112, one or more wireless network interfaces 114(for example, Bluetooth, WiFi or cellular) and one or more non-wirelessinterfaces 116 (for example, a universal serial bus (USB) interface oran HDMI interface).

The electronic device 100 may include an ultrasonic sensing system 118capable of imaging an object signature, such as a fingerprint, palmprint or handprint. In some implementations, the ultrasonic sensingsystem 118 may function as a touch-sensitive control button. In someimplementations, a touch-sensitive control button may be implementedwith a mechanical or electrical pressure-sensitive system that ispositioned under or otherwise integrated with the ultrasonic sensingsystem 118. In other words, in some implementations, a region occupiedby the ultrasonic sensing system 118 may function both as a user inputbutton to control the electronic device 100 as well as a sensor toenable security features such as user authentication based on, forexample, a fingerprint, palm print or handprint.

FIG. 2A shows a block diagram representation of components of an exampleof an ultrasonic sensing system, according to some implementations. Inthe illustrated implementation, an ultrasonic sensing system 200includes a sensor system 202 and a control system 204 electricallycoupled with the sensor system 202. The sensor system 202 may be capableof scanning a target object and providing raw measured image data usableto obtain an object signature of, for example, a human appendage, suchas one or more fingers or toes, a palm, hand or foot. The control system204 may be capable of controlling the sensor system 202 and processingthe raw measured image data received from the sensor system 202. In someimplementations, the ultrasonic sensing system 200 may include aninterface system 206 capable of transmitting or receiving data, such asraw or processed measured image data, to or from various componentswithin or integrated with the ultrasonic sensing system 200 or, in someimplementations, to or from various components, devices or other systemsexternal to the ultrasonic sensing system 200.

FIG. 2B shows a block diagram representation of components of an exampleof an electronic device, according to some implementations. In theillustrated example, an electronic device 210 includes the ultrasonicsensing system 200 of FIG. 2A. For example, the electronic device 210may be a block diagram representation of the electronic device 100 shownin and described with reference to FIG. 1 above. The sensor system 202of the ultrasonic sensing system 200 of the electronic device 210 may beimplemented with an ultrasonic sensor array 212. The control system 204of the ultrasonic sensing system 200 may be implemented with acontroller 214 that is electrically coupled with the ultrasonic sensorarray 212. While the controller 214 is shown and described as a singlecomponent, in some implementations, the controller 214 may collectivelyrefer to two or more distinct control units or processing units inelectrical communication with one another. In some implementations, thecontroller 214 may include one or more of a general purpose single- ormulti-chip processor, a central processing unit (CPU), a digital signalprocessor (DSP), an applications processor, an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA) orother programmable logic device (PLD), discrete gate or transistorlogic, discrete hardware components, or any combination thereof designedto perform the functions and operations described herein.

The ultrasonic sensing system 200 of FIG. 2B may include an imageprocessing module 218. In some implementations, raw measured image dataprovided by the ultrasonic sensor array 212 may be sent, transmitted,communicated or otherwise provided to the image processing module 218.The image processing module 218 may include any suitable combination ofhardware, firmware and software configured, adapted or otherwiseoperable to process the image data provided by the ultrasonic sensorarray 212. In some implementations, the image processing module 218 mayinclude signal or image processing circuits or circuit componentsincluding, for example, amplifiers (such as instrumentation amplifiersor buffer amplifiers), analog or digital mixers or multipliers,switches, analog-to-digital converters (ADCs), passive or active analogfilters, among others. In some implementations, one or more of suchcircuits or circuit components may be integrated within the controller214, for example, where the controller 214 is implemented as asystem-on-chip (SoC) or system-in-package (SIP). In someimplementations, one or more of such circuits or circuit components maybe integrated within a DSP included within or coupled with thecontroller 214. In some implementations, the image processing module 218may be implemented at least partially via software. For example, one ormore functions of, or operations performed by, one or more of thecircuits or circuit components just described may instead be performedby one or more software modules executing, for example, in a processingunit of the controller 214 (such as in a general purpose processor or aDSP).

In some implementations, in addition to the ultrasonic sensing system200, the electronic device 210 may include a separate processor 220, amemory 222, an interface 216 and a power supply 224. In someimplementations, the controller 214 of the ultrasonic sensing system 200may control the ultrasonic sensor array 212 and the image processingmodule 218, and the processor 220 of the electronic device 210 maycontrol other components of the electronic device 210. In someimplementations, the processor 220 communicates data to the controller214 including, for example, instructions or commands. In some suchimplementations, the controller 214 may communicate data to theprocessor 220 including, for example, raw or processed image data. Itshould also be understood that, in some other implementations, thefunctionality of the controller 214 may be implemented entirely, or atleast partially, by the processor 220. In some such implementations, aseparate controller 214 for the ultrasonic sensing system 200 may not berequired because the functions of the controller 214 may be performed bythe processor 220 of the electronic device 210.

Depending on the implementation, one or both of the controller 214 andprocessor 220 may store data in the memory 222. For example, the datastored in the memory 222 may include raw measured image data, filteredor otherwise processed image data, estimated PSF or estimated imagedata, and final refined PSF or final refined image data. The memory 222may store processor-executable code or other executablecomputer-readable instructions capable of execution by one or both ofthe controller 214 and the processor 220 to perform various operations(or to cause other components such as the ultrasonic sensor array 212,the image processing module 218, or other modules to performoperations), including any of the calculations, computations,estimations or other determinations described herein (including thosepresented in any of the equations below). It should also be understoodthat the memory 222 may collectively refer to one or more memory devices(or “components”). For example, depending on the implementation, thecontroller 214 may have access to and store data in a different memorydevice than the processor 220. In some implementations, one or more ofthe memory components may be implemented as a NOR- or NAND-based Flashmemory array. In some other implementations, one or more of the memorycomponents may be implemented as a different type of non-volatilememory. Additionally, in some implementations, one or more of the memorycomponents may include a volatile memory array such as, for example, atype of RAM.

In some implementations, the controller 214 or the processor 220 maycommunicate data stored in the memory 222 or data received directly fromthe image processing module 218 through an interface 216. For example,such communicated data can include image data or data derived orotherwise determined from image data. The interface 216 may collectivelyrefer to one or more interfaces of one or more various types. In someimplementations, the interface 216 may include a memory interface forreceiving data from or storing data to an external memory such as aremovable memory device. Additionally or alternatively, the interface216 may include one or more wireless network interfaces or one or morewired network interfaces enabling the transfer of raw or processed datato, as well as the reception of data from, an external computing device,system or server.

A power supply 224 may provide power to some or all of the components inthe electronic device 210. The power supply 224 may include one or moreof a variety of energy storage devices. For example, the power supply224 may include a rechargeable battery, such as a nickel-cadmium batteryor a lithium-ion battery. Additionally or alternatively, the powersupply 224 may include one or more supercapacitors. In someimplementations, the power supply 224 may be chargeable (or“rechargeable”) using power accessed from, for example, a wall socket(or “outlet”) or a photovoltaic device (or “solar cell” or “solar cellarray”) integrated with the electronic device 210. Additionally oralternatively, the power supply 224 may be wirelessly chargeable.

As used hereinafter, the term “processing unit” refers to anycombination of one or more of a controller of an ultrasonic system (forexample, the controller 214), an image processing module (for example,the image processing module 218), or a separate processor of a devicethat includes the ultrasonic system (for example, the processor 220). Inother words, operations that are described below as being performed byor using a processing unit may be performed by one or more of acontroller of the ultrasonic system, an image processing module, or aseparate processor of a device that includes the ultrasonic sensingsystem.

FIG. 3A shows a cross-sectional of an example of an ultrasonic sensingsystem according to some implementations. FIG. 3B shows an enlargedcross-sectional side view of the ultrasonic sensing system of FIG. 3Aaccording to some implementations. In the illustrated example, theultrasonic sensing system 300 may implement the ultrasonic sensingsystem 118 described with reference to FIG. 1 or the ultrasonic sensingsystem 200 shown and described with reference to FIGS. 2A and 2B. Theultrasonic sensing system 300 may include an ultrasonic transducer 302that overlies a substrate 304 and that underlies a platen (a “coverplate” or “cover glass”) 306. The ultrasonic transducer 302 may includeboth an ultrasonic transmitter 308 and an ultrasonic receiver 310.

The ultrasonic transmitter 308 may be configured to generate ultrasonicwaves towards the platen 306, and a target object 312 positioned on theupper surface of the platen 306. In the illustrated implementation theobject 312 is depicted as finger, but any appendage or body part may becontemplated by the present techniques, as well as any other natural orartificial object. In some implementations, the ultrasonic transmitter308 may more specifically be configured to generate ultrasonic planewaves towards the platen 306. In some implementations, the ultrasonictransmitter 308 includes a layer of piezoelectric material such as, forexample, polyvinylidene fluoride (PVDF) or a PVDF copolymer such asPVDF-TrFE. For example, the piezoelectric material of the ultrasonictransmitter 308 may be configured to convert electrical signals providedby the controller of the ultrasonic sensing system into a continuous orpulsed sequence of ultrasonic plane waves at a scanning frequency. Insome implementations, the ultrasonic transmitter 308 may additionally oralternatively include capacitive ultrasonic devices.

The ultrasonic receiver 310 may be configured to detect ultrasonicreflections 314 resulting from interactions of the ultrasonic wavestransmitted by the ultrasonic transmitter 308 with ridges 316 andvalleys 318 defining surface texture of the target object 312 beingscanned. In some implementations, the ultrasonic transmitter 308overlies the ultrasonic receiver 310 as, for example, illustrated inFIGS. 3A and 3B. In some other implementations, the ultrasonic receiver310 may overlie the ultrasonic transmitter 308 (as shown in FIG. 4described below). The ultrasonic receiver 310 may be configured togenerate and output electrical output signals corresponding to thedetected ultrasonic reflections. In some implementations, the ultrasonicreceiver 310 may include a second piezoelectric layer different than thepiezoelectric layer of the ultrasonic transmitter 308. For example, thepiezoelectric material of the ultrasonic receiver 310 may be anysuitable piezoelectric material such as, for example, a layer of PVDF ora PVDF copolymer. The piezoelectric layer of the ultrasonic receiver 310may convert vibrations caused by the ultrasonic reflections intoelectrical output signals. In some implementations, the ultrasonicreceiver 310 further includes a thin-film transistor (TFT) layer. Insome such implementations, the TFT layer may include an array of sensorpixel circuits configured to amplify the electrical output signalsgenerated by the piezoelectric layer of the ultrasonic receiver 310. Theamplified electrical signals provided by the array of sensor pixelcircuits may then be provided as raw measured image data to theprocessing unit for use in processing the image data, identifying afingerprint associated with the image data, and in some applications,authenticating a user associated with the fingerprint. In someimplementations, a single piezoelectric layer may serve as theultrasonic transmitter 308 and the ultrasonic receiver 310. In someimplementations, the substrate 304 may be a glass, plastic or siliconsubstrate upon which electronic circuitry may be fabricated. In someimplementations, an array of sensor pixel circuits and associatedinterface circuitry of the ultrasonic receiver 310 may be configuredfrom CMOS circuitry formed in or on the substrate 304. In someimplementations, the substrate 304 may be positioned between the platen306 and the ultrasonic transmitter 308 and/or the ultrasonic receiver310. In some implementations, the substrate 304 may serve as the platen306. One or more protective layers, acoustic matching layers,anti-smudge layers, adhesive layers, decorative layers, conductivelayers or other coating layers (not shown) may be included on one ormore sides of the substrate 304 and the platen 306.

The platen 306 may be formed of any suitable material that may beacoustically coupled with the ultrasonic transmitter 308. For example,the platen 306 may be formed of one or more of glass, plastic, ceramic,sapphire, metal or metal alloy. In some implementations, the platen 306may be a cover plate such as, for example, a cover glass or a lens glassof an underlying display. In some implementations, the platen 306 mayinclude one or more polymers, such as one or more types of parylene, andmay be substantially thinner. In some implementations, the platen 306may have a thickness in the range of about 10 microns (μm) to about 1000μm or more.

FIG. 4 shows an exploded projection view of an example of components ofan example ultrasonic sensing system according to anotherimplementation. In the illustrated implementation, the ultrasonicsensing system 400 includes an ultrasonic transmitter 408. Theultrasonic transmitter 408 may include a substantially planarpiezoelectric transmitter layer 422 capable of functioning as a planewave generator. Ultrasonic waves may be generated by applying a voltageacross the piezoelectric transmitter layer 422 to expand or contract thelayer, depending upon the voltage signal applied, thereby generating aplane wave. In this example, the processing unit (not shown) is capableof causing a transmitter excitation voltage to be applied across thepiezoelectric transmitter layer 422 via a first transmitter electrode424 and a second transmitter electrode 426. The first and secondtransmitter electrodes 424 and 426 may be metallized electrodes, forexample, metal layers that coat opposing sides of the piezoelectrictransmitter layer 422. As a result of the piezoelectric effect, theapplied transmitter excitation voltage causes changes in the thicknessof the piezoelectric transmitter layer 422, and in such a fashion,generates ultrasonic waves at the frequency of the transmitterexcitation voltage.

The ultrasonic waves may travel towards an object to be imaged (“targetobject”, not illustrated), passing through the platen 406. A portion ofthe ultrasonic waves not absorbed or transmitted by the target objectmay be reflected back through the platen 406 and received by theultrasonic receiver 410, which, in the implementation illustrated inFIG. 4, overlies the ultrasonic transmitter 408. The ultrasonic receiver410 may include an array of sensor pixel circuits 432 disposed on asubstrate 434 and a piezoelectric receiver layer 436. In someimplementations, each sensor pixel circuit 432 may include one or moreTFT or CMOS transistor elements, electrical interconnect traces and, insome implementations, one or more additional circuit elements such asdiodes, capacitors, and the like. Each sensor pixel circuit 432 may beconfigured to convert an electric charge generated in the piezoelectricreceiver layer 436 proximate to the pixel circuit into an electricalsignal. Each sensor pixel circuit 432 may include a pixel inputelectrode 438 that electrically couples the piezoelectric receiver layer436 to the sensor pixel circuit 432.

In the illustrated implementation, a receiver bias (R_(bias)) electrode440 is disposed on a side of the piezoelectric receiver layer 436proximal to the platen 406. The R_(bias) electrode 440 may be ametallized electrode and may be grounded or biased to control whichsignals may be passed to the array of sensor pixel circuits 432.Ultrasonic energy that is reflected from the exposed (upper/top) surface442 of the platen 306 may be converted into localized electrical chargesby the piezoelectric receiver layer 436. These localized charges may becollected by the pixel input electrodes 438 and passed on to theunderlying sensor pixel circuits 432. The charges may be amplified orbuffered by the sensor pixel circuits 432 and provided to the processingunit. The processing unit may be electrically connected (directly orindirectly) with the first transmitter electrode 424 and the secondtransmitter electrode 426, as well as with the R_(bias) electrode 440and the sensor pixel circuits 432 on the substrate 434. In someimplementations, the processing unit may operate substantially asdescribed above. For example, the processing unit may be capable ofprocessing the signals received from the sensor pixel circuits 432.

Some examples of suitable piezoelectric materials that can be used toform the piezoelectric transmitter layer 422 or the piezoelectricreceiver layer 436 include piezoelectric polymers having appropriateacoustic properties, for example, an acoustic impedance between about2.5 MRayls and 5 MRayls. Specific examples of piezoelectric materialsthat may be employed include ferroelectric polymers such aspolyvinylidene fluoride (PVDF) and polyvinylidenefluoride-trifluoroethylene (PVDF-TrFE) copolymers. Examples of PVDFcopolymers include 60:40 (molar percent) PVDF-TrFE, 70:30 PVDF-TrFE,80:20 PVDF-TrFE, and 90:10 PVDR-TrFE. Other examples of piezoelectricmaterials that may be utilized include polyvinylidene chloride (PVDC)homopolymers and copolymers, polytetrafluoroethylene (PTFE) homopolymersand copolymers, and diisopropylammonium bromide (DIPAB).

In some implementations, at least elements of ultrasonic receiver 410may be co-fabricated with sensor pixel circuits 432 configured asthin-film transistor (TFT) circuitry or CMOS circuitry on or in the samesubstrate, which may be a silicon, SOI, glass or plastic substrate, insome examples. For example, a TFT substrate may include row and columnaddressing electronics, multiplexers, local amplification stages andcontrol circuitry.

FIG. 5 illustrates a block diagram of an ultrasonic sensor system,according to an implementation. The ultrasonic sensor system 500 mayinclude an ultrasonic sensor array 502 that includes an ultrasonictransmitter 520, an ultrasonic sensor pixel circuit array 535 and an Rxbias electrode 540. The ultrasonic transmitter 520 may be electricallycoupled with a transmitter driver (“Tx driver”) 568. In someimplementations, the Tx driver 568 may have a positive polarity outputsignal (Tx1(+)) and a negative polarity output signal (Tx2(−))electrically coupled with one or more transmitter electrodes associatedwith the ultrasonic transmitter 520. The Tx driver 568 may beelectrically coupled with a control unit 560 of a sensor controller 570.The control unit 560 may be configured to control various aspects of thesensor system 500, e.g., ultrasonic transmitter timing and excitationwaveforms, bias voltages, pixel addressing, signal filtering andconversion, readout frame rates, and so forth. The control unit 560 mayprovide one or more transmitter excitation signals to the Tx driver 568.The control unit 560 may be electrically coupled with a receiver (Rx)bias driver 562 through, for example, an Rx level select input bus. TheRx bias driver 562 may provide an RBias voltage to the Rx bias electrode540. The control unit 560 may be electrically coupled with one or moredemultiplexers 564. The demultiplexers 564 may be electrically coupledwith a plurality of gate drivers 566. The gate drivers 566 may beelectrically coupled with the sensor pixel circuit array 535 of theultrasonic sensor array 502. The gate drivers 566 may be positionedexternal to the sensor pixel circuit array 535, in some implementations.In other implementations, the gate drivers 566 may be included on acommon substrate with the sensor pixel circuit array 535. Thedemultiplexers 564, which may be external to or included on a commonsubstrate with the sensor pixel circuit array 535, may be used to selectspecific gate drivers 566. The gate drivers 566 may select one or morerows or columns of the sensor pixel circuit array 535. The sensor pixelcircuit array 535, which, in the illustrated implementation, includes anumber of individual ultrasonic sensor pixels 534, may be electricallycoupled with one or more digitizers 572. The digitizers 572 may convertanalog pixel output signals from one or more of the individual sensorpixels 534 to digital signals suitable for further processing within adata processor 574. The data processor 574 may be included (asillustrated) in the sensor controller 570. In other implementations, thedata processor 574 may be external to the sensor controller 570. In theillustrated implementation, the sensor controller 570 may include one ormore data processors 574 that receive data from the sensor pixel circuitarray 535. The sensor controller 570 may provide data outputs to anexternal system or processor, such as an applications processor of amobile device. The data processor 574 may translate the digitized datainto image data of a fingerprint or format the data for furtherprocessing.

Each ultrasonic sensor pixel 534 may include a PMUT element that mayserve as an ultrasonic receiver and/or an ultrasonic transmitter. Eachsensor pixel 534 may also include a sensor pixel circuit that isassociated with the PMUT element. The associated PMUT element mayoverlay each sensor pixel circuit, that is, the associated PMUT elementand the sensor pixel circuit may be included within a common footprintarea. Advantageously, the sensor pixel circuit may be contained in afootprint area that is no larger than a footprint area of the PMUTelement. In some implementations, the ultrasonic transmitter 520 mayinclude a layer of piezoelectric material sandwiched between twotransmitter electrodes and positioned above or below the ultrasonicsensor pixel circuit array 535.

The ultrasonic transmitter 520 may be electrically coupled to and drivenby the transmitter excitation signals by way of the Tx driver 568 togenerate and launch ultrasonic waves. In some implementations, thetransmitter excitation signals may be coupled to one or more electrodesin each PMUT or PMUT array, such as a transmit electrode associated witheach PMUT, to allow the generation and launching of ultrasonic waves. Insome implementations, the PMUTs in the PMUT array may be provided with atransmitter excitation signal that may be applied in common to some orall of the transmit electrodes in the PMUT array to launch asubstantially plane ultrasonic wave.

In some implementations, the control unit 560 may be configured to senda Tx excitation signal to a Tx driver 568 at regular intervals so as tocause the Tx driver 568 to excite the ultrasonic transmitter 520 andproduce one or more ultrasonic waves. The control unit 560 may also beconfigured to send level select input signals through the Rx bias driver562 to bias the Rx bias electrode 539 and allow gating for ultrasonicsignal detection by the ultrasonic sensor pixels 534. One or more of thedemultiplexers 564 may be used to turn on and off the gate drivers 566that cause a particular row or column of the sensor pixel circuit array535 to provide pixel output signals. Output signals from the sensorpixel circuit array 535 may be sent through a charge amplifier, a filtersuch as a resistor-capacitor (RC) filter or an anti-aliasing filter, andthe digitizer 572 to the data processor 574. One or more control lines576 may carry control signals between the sensor controller 570 and theultrasonic sensor array 502.

FIG. 6 illustrates a simplified block diagram of a sensor pixel arraycoupled with pixel readout electronics. In the illustratedimplementation, an ultrasonic sensor pixel array 635 includes sixteenultrasonic sensor pixels 634 arranged in a 4×4 array for an ultrasonicsensor. Each sensor pixel 634 may be associated with a local region ofpiezoelectric sensor material (PSM) and may include a sensor pixelcircuit 636 that includes a peak detection diode D601 and a readouttransistor M603. Many or all of these elements may be formed on or in acommon substrate to form each sensor pixel circuit 636. In operation,the local region of PSM of each sensor pixel 634 may transduce receivedultrasonic energy into electrical charges. The peak detection diode D601may register the maximum amount of charge (the “peak charge”) detectedby the local region of PSM. Each row of the pixel circuit array 635 maythen be scanned, e.g., through a row select mechanism, a gate driver, ora shift register. Each readout transistor M603 may be triggered to allowthe magnitude of the peak charge for each sensor pixel 634 to be read byadditional circuitry, e.g., a multiplexer and an A/D converter of pixelreadout electronics 640. The sensor pixel circuit 636 may include one ormore TFTs (not illustrated) to allow gating, addressing, and resettingof the sensor pixel 634. Each sensor pixel 634 may include a PMUTelement that may serve as an ultrasonic receiver and/or an ultrasonictransmitter. Each PMUT element in a PMUT sensor array may be associatedwith a respective sensor pixel circuit 636 in the sensor pixel circuitarray 635. Pixel input electrode 637 of the sensor pixel circuit 636 maybe used to make electrical connection with one or more electrodes in anoverlying PMUT element.

Each sensor pixel circuit 636 may provide information about a smallportion of the object detected by an ultrasonic sensor system such as,for example, ultrasonic sensor system 500 described in connection withFIG. 5. While, for convenience of illustration, the example shown inFIG. 4 is of a simple 4×4 array, ultrasonic sensors having a resolutionon the order of 500 pixels per inch or higher may be configured with anappropriately scaled structure. The detection area of the ultrasonicsensor system 500 may be selected depending on the intended targetobject. For example, the detection area may range from about 5 mm×5 mmfor a single finger to about 80 mm×80 mm for four fingers. Smaller andlarger areas, including square, rectangular and non-rectangulargeometries, may be used as appropriate, depending on characteristics ofthe target object.

In some implementations that particularly benefit from the presentlydisclosed techniques, a detection area may be 6000 square millimeters orgreater and include one to five million PMUTs, for example. Such largearea ultrasonic sensors may be configured to image multiple fingerssimultaneously and/or image palm prints, entire hands, or similarlysized artificial or natural objects. In the absence of the presentlydisclosed techniques, the TFT layer signal traces may be unable toaccommodate simultaneous operation of such a large number of PMUTs. Moreparticularly, receiver signal outputs, resulting from localizedelectrical charges generated by the piezoelectric receiver layer andcollected by the pixel input electrodes, may be degraded when a verylarge number of PMUT receivers are operating simultaneously.

To mitigate the above-mentioned problem, in some implementations, atemporal phasing is employed so as to avoid simultaneously outputting anexcessive number of receiver signals. For example, in someimplementations, an ultrasonic pulse may be produced by starting andstopping the transmitters of PMUT array during a short interval of time(e.g. less than 1 microsecond). In such implementations, acousticsignals returned to the PMUT array (resulting from interaction with, forexample, a target object) may be temporally phased so that PMUTreceivers at different locations in the array receive the returnedacoustic signals at different times. Alternatively or in addition, theultrasonic pulses outputted by the PMUT transmitters may be temporallyphased.

Features and benefits of the disclosed techniques may be betterappreciated by referring to FIG. 7, which graphically illustrates anexample of transmitter excitation signals and receiver bias voltagelevels as a function of time. The transmitter excitation signals (uppergraph) may be provided to an ultrasonic transmitter, whereas thereceiver bias voltage (lower graph) may be applied to an RBias electrodeof an ultrasonic sensor element. For example bias voltage levels may beapplied to the RBias electrode 440 (FIG. 4) or 540 (FIG. 5) of anultrasonic sensor array. One or more cycles of an ultrasonic transmitterexcitation signal may be applied to the ultrasonic transmitter, as shownin the upper graph of FIG. 7. In some implementations, a singletransmitter excitation cycle may be used. In some implementations, asillustrated, multiple excitation cycles may be used, such as two cycles,three cycles, four cycles, five cycles or more. The transmitterexcitation signals in some implementations may be square waves,rectangular waves, partial waves, pulsed waves, multiple-frequencywaves, chirped waves, low or high duty-cycle waves, variable-amplitudewaves, variable-frequency waves, or other suitable waveform for drivingan ultrasonic transmitter (e.g., ultrasonic transmitter 408 of FIG. 4 orultrasonic transmitter 520 of FIG. 5). During a first portion of time(“Tx Block”) when transmission of the outgoing ultrasonic wave isoccurring, the bias voltage applied to the RBias electrode maycorrespond to a “block value” such that the receiver bias electrodeprevents signals reflected from outgoing transmitted waves from beingcaptured by a sensor pixel circuit (e.g., sensor pixel circuit 636 ofFIG. 6).

During a subsequent portion of time (“Rx Sample”), the bias level of thecontrol signal applied to the RBias electrode is set to a “sample value”and the reflected ultrasonic signals may be captured a sensor pixel. TheRx Sample period may start upon completion of a range gate delay (“RGD”)period. The RGD period may typically be less than one microsecond. Insome implementations, the RGD period may be about 500 nanoseconds. Theduration of the Rx sample period may be referred to as the range gatewindow (“RGW”) period. The RGW period may typically be less than onemicrosecond. In some implementations, the RGW period may be in the rangeof about 200 to 1000 nanoseconds. To prevent detection of unwantedinternal reflections, the bias level applied to the receiver biaselectrode may be brought back to the block value upon completion of theRGW period. The RGW period, in the illustrated implementation, maycorrespond to a time interval that is roughly similar to the period of atransmitter excitation cycle. In other implementations, the RGW periodmay be shorter or longer than the period of the transmitter excitationcycle. During RGW period, the sensor pixel may be said to be in a “readmode” of operation. During or near the RGW period, the receiver mayoutput signals, resulting from or corresponding to localized electricalcharges generated by the piezoelectric receiver layer and collected bythe pixel input electrodes.

In the absence of the presently disclosed techniques, each of a largenumber of pixels may output receiver signals simultaneously or nearlysimultaneously with a result that at least some signals sufferdegradation due to limitations of the TFT layer signal traces. Tomitigate this problem, the present disclosure contemplates introducingsmall temporal delays between at least portions of the outputtedreceiver signals. As a result, a load on the TFT layer signal traces maybe significantly reduced.

FIG. 8 illustrates an example of temporal phasing of receiver outputsignals, according to an implementation. Referring first to Detail A, aconceptual cutaway view of an ultrasonic sensor system 800 isillustrated, according to an implementation. The ultrasonic sensorsystem 800 includes an array layer 810 of receivers and an array layer820 of transmitters. In order to introduce a delay between the timeultrasound waves are received at each of portions 810(1), 810(2),810(3), 810(4), 810(5), a physical characteristic of a stack of layersin the ultrasonic sensor system 800 is changed in the regions betweentransmitter array 820 and the portions 810(1), 810(2), 810(3), 810(4),810(5), where the change in physical characteristic results in apropagation delay in the ultrasound signal before being received at eachof portions 810(1), 810(2), 810(3), 810(4), 810(5). In the illustratedimplementation, the array layer 820 is not parallel with the array layer810. As a result, the separation distance between receivers of array 810and the array 820 is not uniform. Hence, in the illustratedimplementation, the physical characteristic that is changed in eachregion between transmitter array 820 and each of portions 810(1),810(2), 810(3), 810(4), 810(5) is the physical distance betweentransmitter array 820 and each of 810(1), 810(2), 810(3), 810(4),810(5). The variation in physical distance results in a delay in thereception of the ultrasound wave signal at each of portions 810(1),810(2), 810(3), 810(4), 810(5) after the signal has reflected off of theplaten surface. More particularly, the separation between a firstportion 810(1) of receivers in array 810 and the array 820 is smallerthan the separation between a second portion 810(2) of receivers inarray 810 and the array 820. Similarly: the separation between thesecond portion 810(2) of receivers and the array 820 is smaller than theseparation between a third portion 810(3) of receivers and the array820; the separation between the third portion 810(3) of receivers andthe array 820 is smaller than the separation between a fourth portion810(4) of receivers and the array 820; and the separation between thefourth portion 810(4) of receivers and the array 820 is smaller than theseparation between a fifth portion 810(5) of receivers and the array820. As a result, and as illustrated in Detail B, acoustic signals, thatmay be launched simultaneously by the array 820 reach different portions810(i) of the array of receivers at different times. Each portion 810(i)may correspond to a number of pixel elements. For example, in someimplementations, each portion 810(i) includes a number of rows of pixelelements. In the illustrated example, if the ultrasonic array 800includes an M×N array of ‘M’ rows and ‘N’ columns, each portion 810(i)may include approximately m/5 rows. In other implementations, eachportion 810(i) may include approximately m/10 or m/20 rows, for example.

In the example implementation illustrated in Detail A, a wedge shapeddelay line is obtained by a correspondingly wedge-shaped acoustic layer830 that defines a linearly varying distance between the array 810 andthe array 820. The acoustic layer 830 may be composed of a glass orplastic for example. It will be appreciated that an acoustic layer maybe configured in other shapes than the illustrated wedge-shapedconfiguration to provide non-uniform separation between an array ofreceivers and an array of transmitters. For example, a stair steparrangement, or a curvilinear configuration may be contemplated.Referring now to Detail B, it may be observed that a temporal delay isestablished in the reception of acoustic signals at adjacent portions ofthe array 810. For example, the temporal delay between reception ofacoustic signals at the first portion 810(1) and the second portion810(2) is Δt₁. Similarly: the temporal delay between reception ofacoustic signals at the second portion 810(2) and the third portion810(3) is Δt₂; the temporal delay between reception of acoustic signalsat the third portion 810(3) and the fourth portion 810(4) is Δt₃; andthe temporal delay between reception of dammit acoustic signals at thefourth portion 810(4) and the fifth portion 810(5) is Δt₄. The temporaldelays Δt₁, Δt₂, Δt₃, and Δt₄ may be in the range of a few tens tohundreds of nanoseconds. In an implementation, temporal delays may be5-10% of the transmitter excitation cycle duration, for example, orabout 25-50 nanoseconds. In some implementations, Δt₁, Δt₂, Δt₃, and Δt₄may be approximately equal, but this is not necessarily so. Although thephysical characteristic for introducing a delay in propagation time forthe ultrasound signal that was varied in the illustrated embodiment ofFIG. 8 was a physical distance between transmitter array 820 andportions 810(1), 810(2), 810(3), 810(4), 810(5), it is understood thatthe physical distance could remain constant (i.e., transmitter array 820and receiver array 810 could be parallel), and another physicalcharacteristic of one or more layers in the stack in each region betweenthe transmitter array 820 and each of portions 810(1), 810(2), 810(3),810(4), 810(5) could alternatively be changed in order to introduce thepropagation delay. For example, the physical characteristic forintroducing a delay in propagation time for the ultrasound signal canalso include any physical characteristic capable of affecting the speedof the ultrasonic signal in the stack of layers between transmitterarray and each of portions 810(1), 810(2), 810(3), 810(4), 810(5),including for example, the elasticity of one or more materials (such asby changing, for example, the bulk modulus or Young's modulus) in thestack, the density of one or more materials in the stack, and/or thenumber of interfaces the stack. For example, glass can be doped to havedifferent speeds of sound within it. Hence, the glass between thetransmitter array 820 and each of portions 810(1), 810(2), 810(3),810(4), 810(5) could be doped differently (or could otherwise comprisedifferent materials each) such that even if transmitter array 820 andreceiver array 810 are parallel, each of portions 810(1), 810(2),810(3), 810(4), 810(5) would receive the ultrasound signal at adifferent time from the other portions.

Alternatively or in addition to providing a non-uniform separationbetween an array of receivers and an array of transmitters, the array oftransmitters may be segmented, and a temporal delay provided betweentransmission of acoustic signals from adjacent segments.

FIG. 9 illustrates an example of temporal phasing of transmission andreception of acoustic signals, according to an implementation. Referringfirst to Detail C, a conceptual cutaway view of an ultrasonic sensorsystem 900 is illustrated, according to an implementation. Theultrasonic sensor system 900 includes an array 910 of receivers and anarray 920 of transmitters. In the illustrated implementation, the array920 is approximately parallel with the array 910, but this is notnecessarily so.

The array 920 of transmitters is segmented into separately controlledportions 920(i) that may be configured to undergo, non-simultaneoustransmitter excitation cycles. As a result, and as illustrated in DetailD, acoustic signals may be launched at different times from each portion920(i). As a result, acoustic signals reach portions 910(i) of the arrayof receivers at different times. Each portion 910(i) may correspond to anumber of pixel elements. For example, in some implementations, eachportion 910(i) includes a number of rows of pixel elements. In theillustrated example, if the ultrasonic array 900 includes an M×N arrayof ‘M’ rows and ‘N’ columns, each portion 910(i) may includeapproximately m/5 rows. In other implementations, each portion 910(i)may include approximately m/10 or m/20 rows, for example.

Referring now to Detail D, it may be observed that a temporal delay isestablished in the reception of acoustic signals at adjacent portions ofthe array 910. For example, the temporal delay between reception ofacoustic signals at the first portion 910(1) and the second portion910(2) is Δt₅. Similarly: the temporal delay between reception ofacoustic signals at the second portion 910(2) and the third portion910(3) is Δt₆; the temporal delay between reception of acoustic signalsat the third portion 910(3) and the fourth portion 910(4) is Δt₇; andthe temporal delay between reception of acoustic signals at the fourthportion 910(4) and the fifth portion 910(5) is Δt₈. The temporal delaysΔt₅, Δt₆, Δt₇, and Δt₈ may be in the range of a few tens to hundreds ofnanoseconds. In an implementation, temporal delays may each be 5-10% ofthe transmitter excitation cycle duration, for example, or about 25-50nanoseconds. In some implementations, Δt₅, Δt₆, Δt₇, and Δt₈ may beapproximately equal, but this is not necessarily so.

As indicated above, in connection with FIG. 7, a range gate window (RGW)may be established by setting an Rbias voltage level to a sample value.A sensor controller (e.g. sensor controller 570 of FIG. 5) may beconfigured to set the Rbias voltage level to the sample value. FIG. 10graphically illustrates an example of transmitter excitation signals andreceiver bias voltage levels as a function of time. As the illustratedexample shows, in the absence of the presently disclosed techniques, anRGW period that is well aligned with acoustic signals received by thefirst portion 810(1) of receivers in array 810 (Detail E) is less wellaligned with acoustic signals received by the second portion 810(2) ofreceivers in array 810 (Detail F), and misaligned with acoustic signalsreceived by the third portion 810(3) (Detail G) and the fourth portion810(4) (Detail H) of receivers in array 810.

The present inventors have appreciated that the above noted problem canbe mitigated by establishing a “sliding range gate” mode of operation.FIG. 11 illustrates a sliding range gate, in accordance with animplementation. In the illustrated implementation, a range gate delay(RGD) value is not uniform for all portions of receivers in the array.Consequently, RGW periods may start, for different portions of thereceivers, at different moments in time. In the illustrated example, afirst portion of receivers, e.g., portion 810(1) of array 810, has anRGW period that starts at time RGD(1); a second portion of receivers,e.g., portion 810(2) of array 810, has an RGW period that starts at atime RGD(2)=RGD(1)+Δt₉; a third portion of receivers, e.g., portion810(3) of array 810, has an RGW period that starts at a timeRGD(3)=RGD(2)+Δt₁₀; a fourth portion of receivers, e.g., portion 810(4)of array 810, has an RGW period that starts at a timeRGD(4)=RGD(3)+Δt₁₁. In the illustrated implementation, temporal delaysΔt₉. Δt₁₀. and Δt₁₁ are approximately equal, but this is not necessarilyso. In an implementation, temporal delays Δt₉. Δt₁₀. and Δt₁₁ may eachbe 5-10% of an RGW period. In an implementation, temporal delays Δt₉.Δt₁₀. and Δt₁₁ may be each approximately 25-50 nanoseconds.

In an example implementation, an ultrasonic sensor array may include anM×N array of ‘M’ rows and ‘N’ columns. For example, a 1200×1600 array ofnearly two million pixels may be contemplated. As a further example, a1600×1800 array of nearly three million pixels may be contemplated. Insome implementations, pixel rows are grouped in portions that include5-25% of all rows. For example, for the 1200×1600 array, it may becontemplated to group the 1200 rows into ten portions, each portionincluding 120 rows. In such an implementation, a first portion of 120rows may output receiver signals during an RGW that follows an RGD of,for example, 500 nanoseconds. A second portion of 120 rows may outputreceiver signals during a RGW that follows an RGD of, for example, 525nanoseconds. A third portion of 120 rows may output receiver signalsduring a RGW that follows an RGD of, for example, 550 nanoseconds.Similarly, each successive one of the ten portions may be configured tohave an RGW that is delayed by an additional 25 nanoseconds with respectto an immediately preceding portion. The tenth portion, accordingly, mayoutput receiver signals during a RGW that follows an RGD of, 725nanoseconds. Thus, each RGW is shifted (or “slid”) temporally withrespect to adjacent RGWs.

The sliding range gate mode of operation illustrated in FIG. 11 may beestablished by a sensor controller (e.g., sensor controller 570 of FIG.5) for an ultrasonic sensor array (e.g., ultrasonic sensor array 502 ofFIG. 5) including a number of ultrasonic sensor pixels (e.g., ultrasonicsensor pixels 534 of FIG. 5). As described above each sensor pixel mayinclude a piezoelectric receiver layer (e.g., receiver layer 436 of FIG.4) and a receiver bias electrode (e.g., receiver bias electrode 540 ofFIG. 5). Each sensor pixel may be operable in one or both of a transmitmode of operation or a read mode of operation. The sensor controller,being electrically coupled with the receiver bias electrodes, may beconfigured to set, at each sensor pixel a RGW by applying to arespective receiver bias electrode, a modulated voltage bias thatenables or disables the read mode of operation. The sensor controllermay be further configured to establish different RGWs for differentportions of the ultrasonic sensor array. More particularly, for example,the sensor controller may be configured to set, for a first portion ofthe ultrasonic sensor pixels, a first RGW and to set, for a secondportion of the ultrasonic sensor pixels, a second RGW, and to establisha first temporal delay between the first RGW and the second RGW. Moregenerally, where each portion is identified by an integer, ‘k’, the RGWof each portion k+1 may be delayed with respect to the RGW of portion kby a temporal delay.

FIG. 12 graphically illustrates an example of transmitter excitationsignals and receiver bias voltage levels as a function of time, inaccordance with an implementation. As the illustrated example shows, thepresently disclosed techniques provide an RGW period that is wellaligned not only with acoustic signals received by the first portion810(1) of receivers in array 810 (Detail J) but also with acousticsignals received by the second portion 810(2) (Detail K) the thirdportion 810(3) (Detail L) and the fourth portion 810(4) (Detail M) ofreceivers in array 810.

Although a portion of receivers, as the term is used herein, could be assmall as one receiver, a size of each portion may advantageously beselected to be 5-25% of the total number of receivers for an array ofthe size contemplated by the present disclosure. For example, for a1200×1600 array, ten portions of about 120 rows each may each have arespective RGW. The incremental delay step size between the start ofeach successive RGW may be about 25 nanoseconds in some implementations.As a result, each portion's RGW is not more than 25 nanoseconds from anoptimal temporal location. The incremental delay step size between startof each successive RGW may be constant some implementations. In otherimplementations a variable incremental delay step size may becontemplated.

In the graphs depicted in FIG. 12, the RGD period starts, for eachportion, at the same time, whereas the length of the RGD periodgradually increases, so as to delay the start of the RGW period(comparing the RGW period of the second portion, Detail K, with the RGWperiod of the first portion, Detail J, for example). Alternatively or inaddition, the start of one or more RGB periods may be delayed byincreasing the duration of a preceding hold period. FIG. 13 graphicallyillustrates an example of transmitter excitation signals and receiverbias voltage levels as a function of time, in accordance with such animplementation. In the illustrated example, a start of each RGD isdelayed, with respect to a preceding RGD. In the illustrated example,the duration of each RGB is approximately equal, but this is notnecessarily so.

FIG. 14 illustrates an example of a process flow for operating anultrasonic sensor array. As described hereinabove, the ultrasonic arraymay include a first portion of ultrasonic sensor pixels and a secondportion of ultrasonic sensor pixels. The method 1400 includes a block1410 of setting, with a sensor controller, a first range gate window(RGW) for the first portion of ultrasonic sensor pixels. As describedhereinabove, each sensor pixel may include an ultrasonic receiver and areceiver bias electrode and is operable in one or both of a transmitmode of operation or a read mode of operation. The sensor controller maybe electrically coupled with the receiver bias electrodes. Setting thefirst RGW may include modulating a bias voltage applied to the receiverbias electrode.

At block 1420, the sensor controller sets a second RGW for the secondportion of ultrasonic sensor pixels so as to establish a first temporaldelay between the first RGW and the second RGW. The ultrasonic sensorarray may be configured to establish a temporal phasing of acousticsignals returned, as a result of interaction with a target object, tothe ultrasonic sensor array such that the first portion of theultrasonic sensor pixels receives the returned acoustic signals at adifferent time than the second portion of the ultrasonic sensor pixels.

Optionally, the method 1400 may include setting, at block 1430, for eachof a plurality of portions of the ultrasonic sensor pixels, a respectiveRGW. Optionally, the method 1400 may further include establishing, atblock 1440, a respective temporal delay between each respective RGW.

Alternatively or in addition the method 1400 may optionally includesetting, at block 1450 a respective range gate delay (RGD) with thesensor controller, for each of a plurality of portions of the ultrasonicsensor pixels.

Thus, a sliding range gate for a large area ultrasonic sensor has beendisclosed. It will be appreciated that a number of alternativeconfigurations and operating techniques may be contemplated.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c.

The various illustrative logics, logical blocks, modules, circuits andalgorithm processes described in connection with the implementationsdisclosed herein may be implemented as electronic hardware, computersoftware, or combinations of both. The interchangeability of hardwareand software has been described generally, in terms of functionality,and illustrated in the various illustrative components, blocks, modules,circuits and processes described above. Whether such functionality isimplemented in hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

The hardware and data processing apparatus used to implement the variousillustrative logics, logical blocks, modules and circuits described inconnection with the aspects disclosed herein may be implemented orperformed with a general purpose single- or multi-chip processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general purpose processor may be amicroprocessor or any conventional processor, controller,microcontroller, or state machine. A processor also may be implementedas a combination of computing devices, e.g., a combination of a DSP anda microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration. In some implementations, particular processes and methodsmay be performed by circuitry that is specific to a given function.

In one or more aspects, the functions described may be implemented inhardware, digital electronic circuitry, computer software, firmware,including the structures disclosed in this specification and theirstructural equivalents thereof, or in any combination thereof.Implementations of the subject matter described in this specificationalso may be implemented as one or more computer programs, i.e., one ormore modules of computer program instructions, encoded on a computerstorage media for execution by or to control the operation of dataprocessing apparatus.

If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium, such as a non-transitory medium. The processesof a method or algorithm disclosed herein may be implemented in aprocessor-executable software module which may reside on acomputer-readable medium. Computer-readable media include both computerstorage media and communication media including any medium that may beenabled to transfer a computer program from one place to another.Storage media may be any available media that may be accessed by acomputer. By way of example, and not limitation, non-transitory mediamay include RAM, ROM, EEPROM, CD-ROM or other optical disk storage,magnetic disk storage or other magnetic storage devices, or any othermedium that may be used to store desired program code in the form ofinstructions or data structures and that may be accessed by a computer.Also, any connection may be properly termed a computer-readable medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk, and blu-raydisc where disks usually reproduce data magnetically, while discsreproduce data optically with lasers. Combinations of the above shouldalso be included within the scope of computer-readable media.Additionally, the operations of a method or algorithm may reside as oneor any combination or set of codes and instructions on a machinereadable medium and computer-readable medium, which may be incorporatedinto a computer program product.

Various modifications to the implementations described in thisdisclosure may be readily apparent to those skilled in the art, and thegeneric principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. Thus, the disclosure is not intended to be limited to theimplementations shown herein, but is to be accorded the widest scopeconsistent with the claims, the principles and the novel featuresdisclosed herein. The word “exemplary” is used exclusively herein, if atall, to mean “serving as an example, instance, or illustration.” Anyimplementation described herein as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other implementations.

Certain features that are described in this specification in the contextof separate implementations also may be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation also may be implemented inmultiple implementations separately or in any suitable subcombination.Moreover, although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination may in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed to achieve desirableresults. Further, the drawings may schematically depict one more exampleprocesses in the form of a flow diagram. However, other operations thatare not depicted may be incorporated in the example processes that areschematically illustrated. For example, one or more additionaloperations may be performed before, after, simultaneously, or betweenany of the illustrated operations. In certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system components in the implementations describedabove should not be understood as requiring such separation in allimplementations, and it should be understood that the described programcomponents and systems may generally be integrated together in a singlesoftware product or packaged into multiple software products.Additionally, other implementations are within the scope of thefollowing claims. In some cases, the actions recited in the claims maybe performed in a different order and still achieve desirable results.

It will be understood that unless features in any of the particulardescribed implementations are expressly identified as incompatible withone another or the surrounding context implies that they are mutuallyexclusive and not readily combinable in a complementary and/orsupportive sense, the totality of this disclosure contemplates andenvisions that specific features of those complementary implementationsmay be selectively combined to provide one or more comprehensive, butslightly different, technical solutions. It will therefore be furtherappreciated that the above description has been given by way of exampleonly and that modifications in detail may be made within the scope ofthis disclosure.

What is claimed is:
 1. An apparatus comprising: an ultrasonic sensorarray including a plurality of ultrasonic sensor pixels, each sensorpixel including an ultrasonic receiver and a receiver bias electrode andbeing operable in one or both of a transmit mode of operation or a readmode of operation; and a sensor controller electrically coupled with thereceiver bias electrodes; wherein the sensor controller is configured toset, at each sensor pixel, a range gate window (RGW) by modulating abias voltage applied to the receiver bias electrode; the sensorcontroller is configured to set, for a first portion of the ultrasonicsensor pixels, a first RGW; and the sensor controller is configured toset, for a second portion of the ultrasonic sensor pixels, a second RGW,and establish a first temporal delay between the first RGW and thesecond RGW.
 2. The apparatus of claim 1, wherein the apparatus isconfigured to establish a temporal phasing of acoustic signals returned,as a result of interaction with a target object, to the ultrasonicsensor array such that the first portion of the ultrasonic sensor pixelsreceives the returned acoustic signals at a different time than thesecond portion of the ultrasonic sensor pixels.
 3. The apparatus ofclaim 2, wherein: the ultrasonic receivers are disposed in a receiverarray layer; the ultrasonic sensor array includes ultrasonictransmitters disposed in a transmitter array layer; and the receiverarray layer is not parallel with the transmitter array layer.
 4. Theapparatus of claim 3, wherein a non-uniform separation between thereceiver array layer and the transmitter array layer establishes thetemporal phasing of the returned acoustic signals.
 5. The apparatus ofclaim 2, wherein: the ultrasonic sensor array includes ultrasonictransmitters disposed in a transmitter array layer; the transmitterarray layer is segmented into separate portions; and the sensorcontroller is configured to cause the ultrasonic transmitters to launchacoustic signals, from the separate portions, non-simultaneously so asto establish the temporal phasing of the returned acoustic signals. 6.The apparatus of claim 1, wherein the first RGW has a first RGW durationand the first temporal delay is approximately 5-25% of the first RGWduration.
 7. The apparatus of claim 6, wherein the first RGW duration isbetween 200 nanoseconds and 1000 nanoseconds.
 8. The apparatus of claim1, wherein the first temporal delay is approximately 25 nanoseconds. 9.The apparatus of claim 1, wherein the sensor controller is configured toset, for each of a plurality of portions of the ultrasonic sensor pixelsa respective RGW and to establish a respective temporal delay betweeneach respective RGW.
 10. The apparatus of claim 1, wherein the sensorcontroller is configured to set, for each of a plurality of portions thesensor controller is configured to set a respective range gate delay(RGD).
 11. The apparatus of claim 10, wherein the plurality of portionsincludes a first portion and an adjacent second portion, and wherein theRGD for the second portion is longer than the RGD for the first portionby a temporal delay period.
 12. The apparatus of claim 11, wherein thefirst RGW has a first RGW duration and the temporal delay period isapproximately 5-25% of the first RGW duration.
 13. A method foroperating an ultrasonic sensor array, the ultrasonic array including afirst portion of ultrasonic sensor pixels and a second portion ofultrasonic sensor pixels, the method comprising: setting, with a sensorcontroller, a first range gate window (RGW) for the first portion ofultrasonic sensor pixels; setting, with the sensor controller, a secondRGW for the second portion of ultrasonic sensor pixels so as toestablish a first temporal delay between the first RGW and the secondRGW; wherein each sensor pixel includes an ultrasonic receiver and areceiver bias electrode and is operable in one or both of a transmitmode of operation or a read mode of operation; the sensor controller iselectrically coupled with the receiver bias electrodes; and setting thefirst RGW and the second RGW includes modulating a bias voltage appliedto the receiver bias electrode.
 14. The method of claim 13, wherein theultrasonic sensor array is configured to establish a temporal phasing ofacoustic signals returned, as a result of interaction with a targetobject, to the ultrasonic sensor array such that the first portion ofthe ultrasonic sensor pixels receives the returned acoustic signals at adifferent time than the second portion of the ultrasonic sensor pixels.15. The method of claim 13, further comprising setting, with the sensorcontroller, for each of a plurality of portions of the ultrasonic sensorpixels a respective RGW and establishing, with the sensor controller, arespective temporal delay between each respective RGW.
 16. The method ofclaim 13, further comprising setting, with the sensor controller, foreach of a plurality of portions of the ultrasonic sensor pixels, arespective range gate delay (RGD).
 17. The method of claim 16 whereinthe plurality of portions includes a first portion and an adjacentsecond portion, and wherein the RGD for the second portion is longerthan the RGD for the first portion by a temporal delay period.
 18. Themethod of claim 17, wherein the first RGW has a first RGW duration andthe temporal delay period is approximately 5-25% of the first RGWduration.
 19. A non-transitory computer readable medium storing programcode to be executed by a sensor controller of an ultrasonic sensorarray, the ultrasonic array including a first portion of ultrasonicsensor pixels and a second portion of ultrasonic sensor pixels, theprogram code comprising instructions configured to cause the sensorcontroller to: set, with a sensor controller, a first range gate window(RGW) for the first portion of ultrasonic sensor pixels; set, with thesensor controller, a second RGW for the second portion of ultrasonicsensor pixels so as to establish a first temporal delay between thefirst RGW and the second RGW; wherein each sensor pixel includes anultrasonic receiver and a receiver bias electrode and is operable in oneor both of a transmit mode of operation or a read mode of operation; thesensor controller is electrically coupled with the receiver biaselectrodes; and setting the first RGW and the second RGW includesmodulating a bias voltage applied to the receiver bias electrode. 20.The computer readable medium of claim 19, wherein the ultrasonic sensorarray is configured to establish a temporal phasing of acoustic signalsreturned, as a result of interaction with a target object, to theultrasonic sensor array such that the first portion of the ultrasonicsensor pixels receive the returned acoustic signals at a different timethan the second portion of the ultrasonic sensor pixels.
 21. Thecomputer readable medium of claim 19, further comprising instructions tocause the sensor controller to set, for each of a plurality of portionsof the ultrasonic sensor pixels a respective RGW and establish arespective temporal delay between each respective RGW.
 22. The computerreadable medium of claim 19, further comprising instructions to causethe sensor controller to set, for each of a plurality of portions, arespective range gate delay (RGD).
 23. The computer readable medium ofclaim 22 wherein the plurality of portions includes a first portion andan adjacent second portion, and wherein the RGD for the second portionis longer than the RGD for the first portion by a temporal delay period.24. The computer readable medium of claim 23, wherein the first RGW hasa first RGW duration and the temporal delay period is approximately5-25% of the first RGW duration.
 25. An apparatus comprising: anultrasonic sensor array including a plurality of ultrasonic sensorpixels, each sensor pixel including an ultrasonic receiver and areceiver bias electrode and being operable in one or both of a transmitmode of operation or a read mode of operation; and, electrically coupledwith the receiver bias electrodes, means for controlling the ultrasonicsensor array, the means configured to: set, at each sensor pixel, arange gate window (RGW) by modulating a bias voltage applied to thereceiver bias electrode; set, for a first portion of the ultrasonicsensor pixels, a first RGW; and set, for a second portion of theultrasonic sensor pixels, a second RGW, and establish a first temporaldelay between the first RGW and the second RGW.
 26. The apparatus ofclaim 25, wherein the apparatus is configured to establish a temporalphasing of acoustic signals returned, as a result of interaction with atarget object, to the ultrasonic sensor array such that the firstportion of the ultrasonic sensor pixels receives the returned acousticsignals at a different time than the second portion of the ultrasonicsensor pixels.
 27. The apparatus of claim 26, wherein: the ultrasonicreceivers are disposed in a receiver array layer; the ultrasonic sensorarray includes ultrasonic transmitters disposed in a transmitter arraylayer; and the receiver array layer is not parallel with the transmitterarray layer.
 28. The apparatus of claim 27, a non-uniform separationbetween the receiver array layer and the transmitter array layerestablishes the temporal phasing of the returned acoustic signals. 29.The apparatus of claim 26, wherein: the ultrasonic sensor array includesultrasonic transmitters disposed in a transmitter array layer; thetransmitter array layer is segmented into separate portions; and themeans for controlling the ultrasonic sensor array is configured to causethe ultrasonic transmitters to launch acoustic signals, from theseparate portions, non-simultaneously so as to establish the temporalphasing of the returned acoustic signals.
 30. The apparatus of claim 25,wherein the means for controlling the ultrasonic sensor array isconfigured to set, for each of a plurality of portions of the ultrasonicsensor pixels a respective RGW and to establish a respective temporaldelay between each respective RGW.